The southern pupfish, also known as the southern catfish, is native to the Atlantic coast from North Carolina down to North Florida, as well as along the southern coast of Texas. These fish are commonly found in estuaries and coastal areas. In the fall, adult fish migrate from brackish or freshwater environments into the sea. Depending on temperature and gonadal development, they can begin spawning as early as December, with the main spawning season lasting from late January to February. After spawning, they return to rivers or brackish waters, where their larvae feed on zooplankton along the coast. The larvae undergo metamorphosis after about 60 days.
The southern catfish is a highly valued species worldwide due to its wide temperature tolerance, fast growth rate, and large habitat range. It can thrive in both saltwater and freshwater environments, and it exhibits better resistance to extreme temperatures compared to other species like the gudgeon.
Successful breeding of southern catfish seedlings requires careful management of several factors, including algae inoculation, green water cultivation, rotifer and algae farming, temperature and light control, bait transition, gender regulation during metamorphosis, and prevention of albinism. Here's a brief overview of the seedling rearing techniques used in the south:
1. Prepare the incubation room with equipment for egg hatching. Maintain water quality through regular disinfection, keeping the water temperature between 17°C and 21°C, and salinity at 18‰ to 35‰.
2. Cultivate Chlorella in seawater using sand filtration and bleaching powder for sterilization. Add nutrients such as ammonium sulfate (100g/m³), superphosphate (15–30g/m³), and urea (10–30g/m³). Inoculate the culture and use fluorescent lights at night to enhance light exposure. Maintain a temperature around 20°C. The Chlorella concentration should be around 2,000 to 2,500 cells/mL, serving as food for rotifers.
3. The egg density in hatching depends on water conditions, typically ranging from 250,000 to 350,000 eggs per cubic meter. Micro-inflation is used, and hatching occurs within 3 to 5 days depending on temperature.
4. For early larvae (5–20 days), feed them S-type to L-type Chlorella at a density of 5–10 cells/mL. Regularly add Chlorella to maintain a concentration of 100,000–300,000 cells/mL. Before introducing rotifers, increase Chlorella concentration to 2,500 cells/mL over 6 hours to boost ω3 HUFA levels in rotifers.
5. During the larval stage (20–45 days), start feeding fortified Artemia nauplii at a density of 2–8/mL. At this stage, metamorphosis is nearly complete, and the fish begin to live on the bottom. To increase the female ratio, maintain a temperature of 21°C and keep the density moderate.
6. As juveniles grow, gradually shift their diet. Within 2–3 weeks, reduce rotifer density from 2–8/mL to zero. Use orange-colored Artemia nauplii with a particle size of 250–500μm. This stage marks the transition in bait, and the fish typically reach a length of 2.5cm.
7. Once juveniles reach 2.5cm in length, separate them and move them to juvenile rearing tanks. Introduce copepods at a dose of 0.5–2/mL. Supplement with appropriate amounts of multi-dimensional vitamins, fish oil, and nutrients, ensuring a protein content of 50%–55% and fat content of 6%–14%.
Throughout the entire process, maintaining high water quality is essential, with regular aeration, daily water changes, and thorough cleaning to prevent disease. These practices ensure healthy growth and successful breeding of southern catfish.
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